It is a common problem this monitor has with 7900 video card (if you have something other than 79xx, then you are fine). If you select anything other than "Monitor Scaling" in the nvidia control panel, the monitor will give an error saying "Out of Range". This mean any 4:3 game can only be played stretched.
That 75Hz thing is just something else someone bring up in the eVGA forum. Not quite the same as my main problem :) I am fine with running everything in 60Hz.
When I researching the problem for the 7800gtx (this is before I switched the cable to the other DVI plug- which fixed it for me), I noticed that windows was detecting the native resolution of 1680x1050 at 75 hertz. I tried tinkering with powerstrip to create a custom driver to make the max 60hertz, but I never got it to work.
I read on some forum (I did a lot of reading to try and troubleshoot the problem, but no one had a solution) that if they plugged in a different monitor after outputting the special scaling - it would report the resolution at 1680 x 1050 at 75 hertz. I believe it is a monitor driver problem (or whatever controls the native resolution - I think the monitor reports it also).
On my 7800gtx, I was able to switch the dvi cord to the other plug and it worked afterwards - now windows reports the correct native resolution (and the scaling works great). Unfortantly, LostHere has already confirmed it doesn't work with the 7900s.